Tuesday, October 11, 2016

Let There be Heat!

The Problem. The delivery trip of Shoal Survivor, from Deltaville, VA to Deale, MD
took place between Christmas and New Year's (2008-2009); while it was
actually quite comfortable at the helm during the day, protected behind
the windscreen, it was decidedly chilly watching movies at night, and my
daughter and I vowed that we would install heat before the first frost
visited us in the next winter.

The Solution.
I belabored the different types of heaters at length. We already had
propane, and a spare propane tap existed. The boat was equipped with
propane leak detectors and a solenoid valve, further simplifying the
decision. I had a fair idea of the BTU requirement, having spent a few
nights on the boat last winter when the temperature dropped into the
20s. I learned that a single 1500 watt space heater didn't quite do it
at all and two were just about right. I learned that a vented heater was
an absolute requirement, as even cooking with propane in a sealed cabin
brought on a slight headache; I'm not certain whether it was lack of
oxygen or carbon monoxide. Applying an appropriate conversion factor
(about 3.3 BTUs/watt) and estimating the thermal efficiency at 85%), 5,800 BTUs seem to be the minimum requirement, and perhaps 10,000 BTUs would serve better. The Sig Marine / Dixon P-9000 (5500-7500 BTU output) seemed a reasonable choice and was also the most
we really have room for. A 10 pound bottle of propane should last
50-70 hours, depending on the rate, or most of a season for a $12
refill.

I taped a cardboard of the approximate sized to the wall and we lived with it all summer to prove that it was not in the way.

Note on photo: there is a
short gap above the heater, between the heater and the air intake pipe.
Installation was not finished yet and this was later sealed with a metal band.

Our Experience.

Note 2-19-2010.
Winter experience has proven the above numbers. We burned through 20
pounds in 14 very cold December - February days and nights on the boat. I
except when on the hook, I have turned the gas off at night and used
dock power to run a single 1500 watt space heater. On one very windy 22F
night I had to run the heater on low and 2 x 1500 watt heaters in order
to keep the entire boat over 70F. I turned the gas off to sleep.

Note 3-24-2013.
3-day cold weather trip (27F-46F). Heater ran most of the time
(sometimes on low), plus cooking, and burned about 2-3 pounds each 24
hours. It was off when we left the boat, generally for about 3-6 hours
per day.

Installation. While not overly difficult, gas always require meticulous attention to detail. There are Reasoner that on dry land, most jurisdictions no longer allow gas repair and installation parts to be sold to unlicensed individuals. Please be careful, and read-up on the code.

The gas line must run through a vapor-tight fitting from the propane
locker into the cabin. This is a standard item through West Marine,
Defender Marine, or Sig / Dickson. The hose is typically pre-assembled
with 3/8" flare fittings on each end, so it is a bit fat. The
vapor-tight fitting will accommodate this.

12 volt electric is
required for the fan. The unit will run without it, but the heat output
will be somewhat less and it will not be as well distributed. This is
another reason we chose this over the Cozy Cabin Heater. The shut-off
safety is not dependent on electricity.

Installation side clearances are actually quite small for this unit, because the fan circulatescold
air around the firebox. Additionally, the combustion air is drawn
through the deck, and around the flu via a double wall pipe. Thus,
smokestack never really gets hot on the outside. The required clearance
around the firebox is only 2 inches, and a little bit more around the
smokestack. The smoke stack is almost cool enough to hold in your hand
by the time it reaches the deck, so no special insulation is needed. The
back of the stove and surfaces only a few inches away stay quite cool
and no discernible heat is transferred to the bulkhead.

Mounting. I suppose I could have simply placed screws in the wall, but
it's rather heavy and I decided through bolting made more sense. The
backside ( visible inside the head) fold heads are covered with
decorative caps matching those used throughout the boat, and I used
acorn nuts and on the heater side of the bolts. The holes were
over-drilled, filled with epoxy, and re-drilled. ahead is a shower
compartment as well and thus is quite wet. The bulkhead is foam cored.

Through-deck hole for the smokestack. This was the most stressful step,
I assure you. Boring a 3 1/2-inch, gaping hole through the deck and
through the salon roof and extremely visible place - not relaxing at all
the first time you commit this sort of surgery on the new boat. It went
smoothly enough. After drilling the core was removed extending about
1/2-inch back from the edges and the space filled with epoxy thickened
with Cabosil (fumed silica) to a peanut butter consistency. The small
holes for the mounting screws were also over drilled and, epoxy-filled,
and then re-drilled as well. The smokestack comes with a very thick
rubber gasket that is not drilled for the mounting screws; the screws
drill their own holes through the rubber and make a very tight fit.

Heat and epoxy. It is perfectly acceptable to use moderate heat to
encourage epoxy to cure more quickly in cool weather. However, there are
some caveats: Do not apply significant heat before the epoxy reaches a
gel state, as it will become very runny; do not heat thick layers until
you are certain they will not exotherm and get hot on their own; it is
better to warm the substrate than either the epoxy or the curing mixture
after it has gelled.

Passing the electric wires and gas lines
through the bulkhead near the heater was quite simple. I purchased an
assortment set of rubber grommets from Home Depot; the largest and
second largest nested fit the gas line, and the smallest one
accommodated the 2 x 16 gauge wires.

There is a gap in the flue
in the picture - that was covered by a collar, not yet installed, that
allows for deck movement.Remember that distance between the heater and
the roof changes as you go through waves and as people walk on the deck
There is also thermal expansion to consider. Provide for some movement.

I checked for gas leaks with diluted dish washing liquid and a brush. I have added a simple carbon monoxide detector.

Note:
as of 1-13-2010 the CO monitor has never chirped. There is no odor,
moisture, or other side effect. Just like my home gas furnace, in
miniature.

The optional stack heat shield seems
unnecessary. The stack stays pretty cool (maximum175 F with infrared
thermometer - hurts, but would not burn very quickly). Also, the guard
will only fit if the stack is straight.

The deck guard is necessary; the stack (deck cap, included with the
heaters and pictured to the left) is a VERY effective sheet grabber and
will foul your sheets on every tack. I built a similar custom guard from
1/8" x 3/4" aluminum strap that stands 5" high by 12" across, since the
custom guard from Dickson was not streamlined enough to effectively
shed sheets.

Distributing the heat. We direct a small
pre-existing fan (at first a Hella Turbo, now a Camaro Bora), set on
low, at the stack and heater, blowing downwards. It increases the heater
out-put by cooling the pipe and exterior, and helps spread the heat
evenly throughout the cabin, floor to ceiling, without producing an
objectionable draft. I'm sure location is critical, so experiment with
your geometry.

About
five hours of labor, overall. The only hideous step was drilling the
hole into the propane locker. That involved boat yoga, worming into one
of the under seat lockers in the saloon, which is obviously not
designed for human habitation.

Although the heater
doesn't get hot on the outside, thanks to the fan and jacket
configuration, the glass front gets hot enough to take some paint off
your hand. My daughter has also determined that with the door open and
the flame set on low, it can be used for somores!

I'm
now actually looking forward to our first overnight trip in true winter
weather. I like winter: in the summer, there is a limit as to how many
clothes you can take off; in the winter it is a simple matter to layer
up with modern fleece and stretch products, enough to be comfortable in
anything. My other joy is ice climbing; watch me enjoying a New
Hampshire icefall at ~ -10F... and loving every moment. There is no
swimming in the winter. The wind can howl and often does. Beach combing
is different. Many Bay area businesses close for the season. But it is
still beautiful.

Experience note, 1-13-2010:
operation at the dock and underway has been flawless. Spray and moderate
wind have caused no ill effects. Wind gusts of 25 knots apparent have
caused flame-outs, but the unit interrupted the gas flow quickly. The
heat generally stays in the salon, leaving the cabins quite cool, and so
thick blankets are required. I like it that way. At dock, we use small
electric space heaters on low in the cabins.

Note
on thermal efficiency. The exhaust gases go through a double-pipe heat
exchanger, giving up heat to the incoming combustion air. The draft is
controlled (there is not too much excess air, as the gas flame is
yellow) and waste up the stack is reduced (the maximum stack temperature
is only about 285 F by IR thermometer). Thus, depending on the
assumptions, the of the heater is about 85% efficient , as good as you
will find short of a high-efficiency condensing heater, not available
for boats. Most marine heaters are 70-80% efficient and have much higher
exhaust temperatures.

10-22-2011: I just
returned from another cool weather trip; still working well. As it is a
vented heater, it warms the boat without humidity increase, CO or CO2
risk, and is without odor.

3-24-2013:
Some continuing problems with flame blowing out if sailing with wind on
beam above 20 knots. I need to upgrade the deflector. No problems at
anchor, only with wind on beam.

A simple. dependable solution, without the complications of forced air heat. Not what I would do if I lived aboard, but just fine for the occasional year-round cruiser.

Keeping a Cruising Boat for Peanuts--Available in PDF!

As much as I love sailing, putting my daughter through college and funding my 401K are more important. Transitioning from professional engineer to writer has transformed my habit of living efficiently into a passion for spreading funds thin. I like to think of it as a challenge for the imagination—it’s more fun that way.

I’ve written over 100 equipment reviews and engineering articles for popular sailing magazines, all based on laboratory and hands-on testing. I’ve spent 30 years learning how to maintain, fix, and upgrade. I've also spent 35 years as a chemical engineer, and my wife thinks I live in my basement shop.

As a result I’ve become a fair hand most crafts, never get stuck in the field with something I can’t fix, and I've learned to spread money thin, without compromising speed, reliability, or performance. Although I've written on many topics, my wife assures me this is the one I know best. My magnum opus?

About Me

This is my place to share my enthusiasm for the Chesapeake Bay, Delmarva Peninsula, PDQ And Corsair F-24 specific minutia, and sailing in general. As a regular contributor to sailing magazines including Practical Sailor and Good Old Boat (over 150 articles), it provides a place to try out ideas and publish the overflow. Here I can blurt it out half formed ideas, collect comments, and to see what questions my inquiry suggests. If I need to get long winded or philosophical, it’s my space to do so.
After 15 years of kayaking, 35 years of sailing, 35 years of rock and ice climbing, and 40 years as a chemical engineer, I still have much to learn and my life is still one giant science project. My end of the pier is always festooned with test rigs and warning signs. Every research project brings surprises—things I didn’t know, and just as often, things no one knew. And so through books and articles, I share.